And I'm Linda Wertheimer. Sen. John McCain is pushing the Obama administration to do more for rebels fighting the Syrian government. This follows his trip last week to opposition-held territory in Syria. McCain warns that a failure to act could send the Middle East deep into sectarian conflict.

His comments come as both the rebels, and the likelihood of planned peace talks, appear to be losing ground.NPR's Michele Kelemen reports.

MICHELE KELEMEN, BYLINE: Arizona Republican John McCain says U.S. friends and allies in the Middle East are crying out for American leadership, and want to see a more credible U.S. policy on Syria.

SEN. JOHN MCCAIN: I want a negotiated end to this settlement. So do we all. But anyone who thinks that Assad and his allies will ever make peace when they are winning on the battlefield, is delusional.

KELEMEN: In a speech to the Brookings Institution, McCain said the U.S. needs to tip the balance in favor of the rebels; and he's suggesting setting up a safe zone in Syria, protected by Patriot missiles, where the opposition can organize a provisional government.

The Arizona senator met with Syrian rebels last week, and said they all painted the same picture; that they aren't receiving enough help, but Assad's forces are.

MCCAIN: Assad has turned the tide of battle on the ground. His foreign allies have all doubled down on him. Iran is all in; Russia is in; Shiia militants are flowing in to fight, from Iraq; and Hezbollah fighters have invaded Syria by the thousands.

KELEMEN: They were decisive, McCain said, in retaking the city of Qusair from the rebels this week. He's not the only one expressing deep skepticism about the peace conference that Secretary of State John Kerry and his Russian counterpart, Sergei Lavrov, are trying to arrange.

The idea behind their plan is to get all the parties to the negotiating table, to agree on a transitional government, a plan initially put forward last year in Geneva. Paul Salem, of the Carnegie Endowment for International Peace, says Geneva II won't end the war.

PAUL SALEM: Geneva II is not going to resolve the situation. I think more in terms - in a sense of Geneva 10, in the sense that it's - this is going to take many, many years.

KELEMEN: Salem says the more immediate goal should be to tamp down the violence, and freeze the situation on the ground.

SALEM: Because the actual resolution of this conflict is nowhere in sight. The regime is in no mood to enter any serious negotiation, and the opposition is neither in a position - because it's completely disunited - nor in a mood to make any major compromises. So our objective should be to limit bloodshed and at least main - you know, create a situation in Syria that's more calm and that's more livable.

KELEMEN: His doubts were echoed by Yezid Sayigh, speaking via video hookup from the Carnegie Middle East Center in Beirut. The Carnegie scholar said the opposition has made clear it will only attend a conference in Geneva if Assad is pushed out of the way, but the only thing Assad will accept is a deal that leaves him in place and able to run for office again.

YEZID SAYIGH: I'm not saying that the U.S. is ready to accept this yet, or that the EU is ready to accept this. I'm simply saying, there is no other negotiable solution right now because no one is in a position to dictate to the Syrian regime, or to its allies.

KELEMEN: And the Syrian opposition is in turmoil, says Raphael LeFevre, a Cambridge University scholar. He's been writing about Syria's Muslim Brotherhood, which he predicts will soon break from the opposition coalition.

RAPHAEL LEFEVRE: The international community should perhaps expect the Syrian opposition in general to be more and more fragmented - not to be more and more united - in the run-up to the Geneva II Conference.

KELEMEN: Secretary of State Kerry, though, seems undeterred. His spokesperson, Jen Psaki, says Geneva will happen, once the opposition picks a team to g,o and once the organizers can agree on who else should be there.

JEN PSAKI: The U.N., the U.S. and the Russian representatives will meet again in just a few weeks and continue to work towards setting a date, an agenda; and determining participation.

KELEMEN: Kerry and his Russian counterpart first announced plans for the conference last month, and at the time said they hoped it would happen by the end of May.